WirelessHART

Заказные данные
(5)

WirelessHART is the first international industry standard for wireless communication on the field level in process automation. This means users are offered a standard for wireless communication on the field level for the first time which ensures interoperability of devices and components regardless of the manufacturer.

Область применения

Looking at the large number of possible applications and configurations, we generally differentiate between two application types.

With the first type, the reason is that, according to estimates made by the HART Communication Foundation (HCF), approx. 85% of the more than 30 million HART devices are used in an environment in which only the 4 ... 20 mA interface is used on the system side, but not the HART interface of the device. Generally, data on the device can only be read on site. This is a great disadvantage, especially for devices with functions for self-diagnostics. This is referred to as "stranded diagnostics".

In these cases, a WirelessHART adapter can offer assistance. Connected to the 4 ... 20 mA loop, it allows for wireless and central access to the device. It does not affect older process control systems which continues to receive the measured value using the 4 ... 20 mA-loop.

Central access takes place via a diagnostics station with SIMATIC PDM.

The most important advantages:

Increases the availability of the system
Increases system transparency
Cost reductions through a predictive instead of a preventive maintenance concept
Shorter distances to be covered in larger plants as result of central access to field instrumentation

In the second type of application, the 4 ... 20 mA loop is omitted; all data as well as the process values measured and the diagnostic information are transmitted wirelessly, e.g. to a process control system.

The most important advantages:

No planning and installation of data cables, resulting in sometimes significant cost reductions.
Increased transparency in the plant through additional installation of measuring points, which was previously uneconomical.
Process optimization using flexible, temporary and low-cost measuring points with wireless communication.
Utilization of proven devices by using adapters
Coverage also of longer distances using the meshed WirelessHART network.

Дизайн

Below is a more detailed description of the application types described in the previous section.

The figure below shows a typical situation for the first application type.

The adapter is connected to the 4 ... 20 mA loop, which is used to transmit the measured value to the control system, or transmit the control value to the actuator. This does not affect the control system.

The data, especially the diagnostics data, from the devices is transmitted over the connected adapter and the wireless HART network to the IE/WSN-PA LINK. The link makes this data available over Industrial Ethernet to a diagnostics and maintenance station with installed SIMATIC PDM software. To eliminate the installation costs for the Ethernet cabling, you can use Industrial Wireless LAN. An extensive product spectrum of Scalance W components is available for this purpose.

The existing control system is not affected by the WirelessHART adapter.

The figure below shows a typical situation for the second application type.

WirelessHART is an evolutionary subsequent development of the HART standard

The integration of WirelessHART in SIMATIC systems takes place parallel to the integration of wired devices with HART or PROFIBUS interfaces. The 4 ... 20 mA cable to the control system is omitted in this case: All data, which means process data, parameters, diagnostic information and functions, is made available to the automation system wirelessly. This is mainly important during reconstruction measures and expansion of existing plants and, of course, in new plants, but also for temporary and mobile measurements.

The field devices are standard devices with connected adapters or those with integrated wireless capability.

We basically have to distinguish between wireless communication and power supply of the devices.

When installing a field device, the planning and installation of the data cable to the control system is usually considered a significant cost driver. The costs are significantly reduced through the use of wireless communication.

When using 4-20 mA/HART field devices with adapters, the question of power supply always arises - in contrast to battery-powered field devices with integrated wireless modules. It is important to distinguish between two- and four-wire devices here. Under certain circumstances, the SITRANS AW200 adapter can take over the supply of a connected two-wire device. The power consumption of the field device plays an important role here. If it is too high, an additional power supply becomes necessary. If more than one device is connected to the SITRANS AW200 adapter, an additional power supply is generally required. Four-wire devices always require an additional power supply.

Функции

The properties of WirelessHART can be summarized as follows:

Simple handling and engineering
Safe communication
Availability in network

Simplicity in handling and engineering

Utilize current tools, same workflow
The description of devices and adapter is carried out using proven EDDL technology. SIMATIC PDM continues to be used as a tool.
Multiple options for the device supply
The devices can, for example, be operated with 24 V DC externally, external or integrated battery packs, or solar cells. The option of using energy from the process or the environment has been researched at universities and industry for some time. Results and products can be expected in the medium term.
Reduced installation costs
Depending on use, installation costs for data cables or power supply cables are not required.
Coexistence with other wireless networks
WirelessHART exclusively uses the ISM band in the 2.4 GHz range because it is available worldwide. However, this range is also used by Industrial Wireless LAN
(IWLAN), for example. For this reason, a requirement to allow WirelessHART to co-exist with Wireless LAN networks was an absolute requirement when this technology was defined. This coexistence was accomplished by constantly changing the channels and therefore the frequencies. This change is also referred to as "channel hopping". Moreover, individual channels can be completely blocked with the so-called "black listing" feature if they are used locally, for example, by IWLAN.
Support of star and meshed network topologies
Networks can be set up in star shape as well as meshed. The advantage of star-shaped networks with a gateway as the centre is that it allows for rapid update cycles. However, the expansion of the network is limited to a distance of 200 m without obstacles between gateway and devices.
The advantage of meshed networks is their large expansion, because each station in the network is also a repeater that forwards the data from remote stations in the direction of the gateway. The disadvantage: increased transport times for data between the field device and the gateway.
Faster commissioning
After installation of a device, it can usually be commissioned at once because there is no wait time until installation of the cables is complete.
Self-organizing and self-healing networks
WirelessHART networks are automatically organized, set up and managed by the network manager. Engineering is usually not necessary.
The network manager is implemented in the IE/WSN-PA LINK, which means the Siemens gateway. It calculates the optimal connection paths between the stations in the network and determines in advance an alternative path that can be used in case of an error. The network is self-healing in this respect. It also specifies the channels or frequencies that are to be used for each communication. Statistics regarding communication are also created automatically and are available to the user.
Security - always active
All designated mechanisms with regard to security are available automatically, and do not have to be planned out.
Changes in the network without configuring
Stations are added or removed automatically in the network by the network manager.

Safe communication

Encryption - all data is encrypted with 128-bit AES before it is sent.
Specific keys for each data packet
Data integrity - Each data packet is checked to see if it was changed or damaged during transport.
Device authentication
Each device must know the network identification number as well as the join key. Otherwise, it is not integrated into the network by the network manager.
Channel hopping
The utilized channel is changed according to specifications of the network manager after each telegram. This represents another level of protection from espionage.
Report of faulty authentication
Any failed attempt of a station to integrate itself into the network is recorded and made available to the user.

Availability in network

Communication based on IEEE 802.15.4-2006
The wireless communication takes place based on a proven industry standard. It allows for very minimal power consumption.
Use of the ISM band (2.4 GHz)
This band can be used worldwide without any additional costs.
Channel hopping overcomes interference
Interference is often limited to a small frequency range. By constantly changing the channel, the effects of such interference can be circumvented and the availability of the network can be increased.
Channel black listing permanently blocks faulty channels.
During operation of another network at the same location, the channels occupied by it can be blocked in the WirelessHART network.
Self-healing network
Redundant communication paths
The network manager automatically calculates redundant communication paths. This significantly increases the level of availability.

Software Overview

Applications 1 and 2 will require the following software products.

	Component	Products	Article number
Application type 1	Process Device Manager	SIMATIC PDM and Options	See ordering data SIMATIC PDM
	Process Device Manager	HART OPC server V3.2	Included in SIMATIC PDM¹⁾
	WirelessHART Gateway	IE/WSN-PA Link with integrated non-removable aerial²⁾	6GK1 411-6CA40-0AA0
	WirelessHART adapter	SITRANS AW200²⁾	7MP3112-1AA00-0AA0
	WirelessHART adapter	SIMATIC S7/SIMATIC PCS 7 function blocks for integration of field instruments with WirelessHART and the IE/WSN-PA LINK	9AE4110-3AA00
Application type 2	Process control system	SIMATIC PCS 7
	WirelessHART Gateway	IE/WSN-PA Link with integrated non-removable aerial²⁾	6GK1 411-6CA40-0AA0
	Field devices	SITRANS AW200²⁾	7MP3112-1AA00-0AA0
		SITRANS AW210²⁾	7MP3111-...
		SITRANS P280²⁾	7MP1120-...
		SITRANS TF280²⁾	7MP1110-...

¹⁾ Contact your Siemens contact partner if you have any questions.

²⁾ Other versions and accessories are available in this catalog in the Product description.

Особенности

WirelessHART enables access to the following:

Measuring and control values
Parameters

of field devices with HART interface. These usually include pressure, temperature, level or flow transmitters or actuators.

WirelessHART permits:

wireless transmission of measured values and their status
wireless parameterization and diagnosis of field devices

The Wireless-HART adapter can be used to fit field devices with HART interfaces (that are designed for wired communication) for wireless communication. This lets users continue using their proven devices and still benefit from the advantages of wireless communication.

Дальнейшая информация

More detailed information on the required WirelessHART software and hardware components can be found in the FI 01 catalog or at http://www.siemens.com/wirelesshart.